Add support for Armv8.3-A Pointer Authentication

This patch cherry-picks the following patches for Armv8.3 PAC
extension compatibility.

These have been merged to Android's libunwindstack:
https://android-review.googlesource.com/c/platform/system/core/+/1215022
https://android-review.googlesource.com/c/platform/system/core/+/1403667

Change-Id: I31bfa9219c2d05e8d2e176a02688afa693b69260
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/third_party/libunwindstack/+/2727280
Reviewed-by: Mike Wittman <wittman@chromium.org>
9 files changed